TSETSE FLIES 845 



cover the face of the country in belts sometimes 

 70 or 80 miles across. The bush in district, 

 no matter how dry, is full of them. They bite 

 human beings and animals alike incessantly from 

 sunrise to sunset, and make life on the road one 

 long purgatory. In the case of this insect, 

 therefore, there was no place to which the 

 unhappy people could be removed unless they 

 abandoned the country altogether. To make 

 matters worse, it could not be stamped out by 

 the collection or destruction of its eggs. The 

 tsetse fly does not deposit eggs like the general 

 mass of insects. Its larva is extruded perfect 

 from the oviduct of the female, and is dropped 

 in a shady place, preferably in loose crumbling 

 soil. There it creeps into the earth, grows so 

 dark in colour as to become practically indis- 

 tinguishable from its surroundings, and in a 

 short time turns into the pupal or chrysalis 

 stage. Each female fly, with a lifetime of three 

 or four months, may produce eight or ten of these 

 larva, so that when one comes to reflect upon the 

 propagatory activities of a large belt of tsetse 

 flies, the hopelessness of attempting to extermin- 

 ate them in the undeveloped stage will be readily 

 appreciated. 



The Loangwa Valley commissioners now 

 turned their attention to ascertaining what 

 constituted the host, or main reservoir, of the 

 new sleeping sickness parasite, the Trypanosoma 

 rhodesiense, and to this end began the systematic 

 examination of the blood of a large number of 

 wild and domestic animals, including that of 



